1. Field of the Invention
The present invention relates to a restoration apparatus for a liquid ejection head and an image forming apparatus comprising a restoration apparatus for a liquid ejection head, and more particularly, to an ejection restoration apparatus for nozzles which can be used when a nozzle blockage or the like has occurred in an apparatus which forms an image by ejecting ink onto a recording medium, or the like, and to an image forming apparatus comprising such an ejection restoration apparatus.
2. Description of the Related Art
As an image forming apparatus in the related art, an inkjet printer (inkjet recording apparatus) is known, which comprises an inkjet head (liquid ejection head) having an arrangement of a plurality of liquid ejection nozzles and which records an image on a recording medium by ejecting ink (liquid) from the nozzles toward the recording medium while causing a relative movement between the inkjet head and the recording medium.
The inkjet head of an inkjet printer of this kind has pressure generating units, each comprising, for example, a pressure chamber to which ink is supplied from an ink tank via an ink supply channel, a piezoelectric element which is driven by an electrical signal in accordance with image data, a diaphragm which constitutes a portion of the pressure chamber and deforms in accordance with the driving of the piezoelectric element, and a nozzle which is connected to the pressure chamber and from which the ink inside the pressure chamber is ejected in the form of a droplet because of the volume of the pressure chamber being reduced by the deformation of the diaphragm. In such an inkjet printer, one image is formed on a recording medium by combining dots formed by ink ejected from the nozzles of the pressure generating units.
An inkjet printer of this kind records information by ejecting ink directly from very fine nozzles, and there is a possibility of printing defects caused by ejection defects or ejection failures due to abnormality of the state of the nozzles. Therefore, it is necessary to maintain the ink in a state which allows normal ejection at all times.
In particular, in an on-demand type of inkjet printer which ejects ink only when an image signal is input, there may be nozzles which do not perform ink ejection over a long period of time. In this case, the ink solvent evaporates from the nozzles, the viscosity of the ink increases or the ink dries, and ejection defects may occur. Phenomena of this kind may also occur if a recording operation is not carried out for a long period of time.
In order to prevent ejection defects of this kind, almost all inkjet printers include restoration mechanisms or restoration apparatuses of various types, which remove ink having increased viscosity inside the nozzles and a dried film (of ink) on the nozzle surface, thereby setting the nozzles to a state capable of normal ejection. Moreover, in addition to removing the ink having increased viscosity and the dried film, nearly all restoration mechanisms or restoration apparatuses also have a function for removing foreign matters, such as dust inside the nozzles, and ink, dirt, or the like, adhering to the nozzle surface. More specifically, the following inventions are disclosed as technologies of this kind.
Japanese Patent Application Publication No. 2-179756 discloses a constituent part which includes an ink absorbing device and a wiping device having a blade, and this constituent part can simplify maintenance operations.
Japanese Patent Application Publication No. 6-328729 discloses an ejection restoration apparatus for an inkjet head having a partial suctioning device which suctions ink while abutting against the nozzle surface and performing a wiping movement.
However, in the related art, during the maintenance of the inkjet head, it is necessary to carry out a wiping operation and a suctioning operation by capping, successively, and there is a possibility that the composition becomes complex. Moreover, since a large amount of maintenance time is required in order to carry out these operations, then throughput may decline. Furthermore, if ink is suctioned from the whole of the inkjet head, then there is a large amount of wasted ink.
In the invention described in Japanese Patent Application Publication No. 2-179756, although it is possible to simplify the constituent component, capping and suctioning operations and wiping operations must be carried out individually, and therefore a long time is required for maintenance.
Moreover, in the invention described in Japanese Patent Application Publication No. 6-328729, suctioning by capping is not sufficient. More specifically, if the cap is moved while the suctioning is performed, then the received force differs between the front side and the rear side of the cap in terms of the movement direction of the cap. Since no consideration at all is given to this point in Japanese Patent Application Publication No. 6-328729, then air leakage occurs during the suctioning by means of the cap and it is difficult to carry out sufficient suctioning. Moreover, since no consideration is given to carrying out wiping by a blade moving over the nozzle surface, then the rigidity of the elastic body may be too high and satisfactory wiping may not be achieved by means of the blade, and ink may therefore be left on the nozzle surface.
In cases where the suctioned portion is smaller than the nozzle plate in which the nozzles are arranged, when only a portion of the nozzles are suctioned (suctioning is carried out in one localized area by applying a negative pressure), then the negative pressure is liable to effect on nozzles other than the nozzles being suctioned. Consequently, in other non-suctioned nozzles, the meniscus (an air-liquid interface inside a nozzle created by the surface tension of the liquid) may be withdrawn, and air or gas bubbles may be caused to flow back into pressure chambers.